Not much to suggest in terms of anatomy and such. If I had to say anything maybe it would be to try and improve the line quality. For example, the bathing suit girl is well drawn, however I think the graininess detracts from the picture a bit. Now this is more or less personal preference since some people like the grany effect.

One technique I used to clean my drawings up when I sketched them was to draw it, and then of course the lines would be a little jagged or what have you. So, what I did was, I erased one section at a time (say a shoulder or an arm) but just enough so you could still see where the lines used to be. Then I would redraw what I erased but made an effort to keep it smooth and dark (almost like inking). It worked well for me anyways. I'm weird.